Herbivores can alter plant community through selective grazing. Refuge effects, in which existence of unpalatable plants could reduce grazing effects on other species, were receiving attention for conserving plant community in heavily grazed sites. On Mt. Kushigata in central Japan, semi-natural grassland which had dominant of Iris sanguinea had been seriously grazed by sika deer ( Cervus nippon) since about ten years ago. The aim of this study is to investigate whether the refuge effects on I. sanguinea are found and show what species play an important role of the effects.

In 2011, we investigated species composition, cover, maximum height and bite marks on 254 1x1m-sampling plots located in the grassland. We also recorded soil moisture content, degree of grazing and distances from hiking route and from edge of forests in each plot.

Dominant species of many plots were graminoids, small-sized or unpalatable species. I. sanguinea, palatable and middle-sized species, was also dominant. Height distribution of I. sanguinea was quite variable among plots. From the results of GLM, the height was positively affected with graminoids cover. This result could be explained by two possible reasons: (i) graminoids which had resistance ability against grazing protected I. sanguinea from grazing and (ii) growth of I. sanguinea might be facilitated by competing against graminoids.